BMW Considers Quad-Turbo Diesel Engine

If technological progress can be measured in the number of turbochargers attached to an engine, BMW is doing an amazing job. Already one of the only manufacturers to offer an engine with three turbos, BMW has now announced that it will evolve this concept into a new quad-turbo diesel, which will first see service in the upcoming 2016 750d. Quad-turbo engines certainly aren’t new, Bugatti had a quad turbo production car all the way back in 1991, but BMW is going to be putting four turbos on a six-cylinder engine, and that kind of turbo-to-cylinder ratio is pretty unusual.

BMW hasn’t released any numbers for the engine, which will be designated the B57 TOP, but it isn’t too likely that it will offer a huge horsepower advantage over the current tri-turbo configuration. Expect somewhere around 408 horsepower and about 590 pound feet of torque, not a huge amount for a car the size of a 7 Series, but certainly adequate, and it should deliver a reasonable return as far as fuel economy goes. The turbos are likely there to make the engine more responsive, and to widen the torque curve.

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Why it matters

We’re not sure if these turbo will be the regular sort or if they will be electric, but what we do know is that there will probably be two smaller units for lower revs and two larger units for when the engine gets higher up in the range. It’s actually a pretty normal setup for bi-turbo engine, and this just doubles up on everything.
The tri-turbo works a little differently, with a small turbo for very low revs, a bigger one that kicks in at about 1,500 rpm and then another small one that kicks in along with the bigger one at higher rpm. It’s a strange setup, but it works extremely well, and there’s a very good chance that this new one will too.